Hypselostoma serpa ( van Benthem Jutting, 1950 ), 2025

Hypselostoma serpa ( van Benthem Jutting, 1950) comb. nov.

Figs 224 H View Figure 224 , 234 View Figure 234 , 241 View Figure 241

Paraboysidia serpa van Benthem Jutting, 1950: 18–19, 40, fig. 8. View in CoL

Paraboysidia serpa View in CoL — Maassen 2001: 75.

Paraboysidia tarutao Panha & Burch, 2002 c: 85–87 View in CoL , fig. 4. syn. nov.

Gyliotrachela tarutoa [sic] — Panha and Burch 2008: 84, fig. 73.

Gyliotrachela tarutao View in CoL — Dumrongrojwattana and Wongkamhaeng 2024: 324, fig. 8.

Type material examined.

Malaysia • 18 paratypes of H. serpa ; from the type locality; Dec. 1938; Raffles Museum, Singapore ex. coll.; RMNH.Moll.140164 . Thailand • 1 paratype of G. tarutao ; from the type locality; 1998; S. Panha leg.; CUMZ ver. 062 .

Additional material examined.

Thailand • 22 shells; Krabi Province, Railay (= Rai Leh) Beach West, Railay Highlands , at the base of limestone rocks; 8°0.865'N, 98°50.219'E; 30 m a. s. l.; Sep. 2007; A. Reischütz leg.; coll. REI GoogleMaps • 1 shell; Krabi Province, Phi Phi islands, Phi Phi Don island, climbing rock above the western end of the beach in Ton Sai Bay , at the base of limestone rocks in the forest; 7°44.063'N, 98°45.947'E; 50 m a. s. l.; Mar. 2010; A. Reischütz leg; coll. REI GoogleMaps .

Type localities.

“ Baling, Kedah ”, Malaysia ( H. serpa ); “ Tarutoa National Park, Satul Province, Thailand, 6 ° 41 ' 58 ' N, 99 ° 38 ' 48 ' E, 70 meters elevation ” ( P. tarutao ).

Differential diagnosis.

Hypselostoma serpa is most similar to H. frequens , from which it can be separated by the keeled last whorl (rounded in H. frequens ), the bent upper palatal plica and the wider umbilicus. Hypselostoma kelantanense has a more ovoid shell shape, more rounded and bulging whorls as well as narrower umbilicus.

Distribution.

This species is known from Kedah, Malaysia (the type locality) as well as from Krabi Province and Ko Tarutao Island, Satun province, Thailand (the type locality of G. tarutao ).

Remarks.

In the paratypes, interpalatal plica is simple or bulge like, infraparietal lamella can be present or absent. All examined paratypes have upper palatal plica curved towards the lower one which could be characteristic for this species. Paraboysidia tarutao is treated as a junior synonym of this species since no morphological differences were noticed. In the original description ( Panha and Burch 2002 c), P. tarutao was not compared to H. serpa which gives the impression that the latter was overlooked.